Effects of the acoustic properties of infant-directed speech on infant word recognitiona)

a) Portions of this work were presented at the 154th Meeting of the Acoustical Society of America in New Orleans, LA (2007) and the 32nd Boston University Conference on Language Development in Boston, MA (2007).

Abstract

A number of studies have examined the acoustic differences between infant-directed speech (IDS) and adult-directed speech, suggesting that the exaggerated acoustic properties of IDS might facilitate infants’ language development. However, there has been little empirical investigation of the acoustic properties that infants use for word learning. The goal of this study was thus to examine how 19-month-olds’ word recognition is affected by three acoustic properties of IDS: slow speaking rate, vowel hyper-articulation, and wide pitch range. Using the intermodal preferential looking procedure, infants were exposed to half of the test stimuli (e.g., Where’s the book?) in typical IDS style. The other half of the stimuli were digitally altered to remove one of the three properties under investigation. After the target word (e.g., book) was spoken, infants’ gaze toward target and distractor referents was measured frame by frame to examine the time course of word recognition. The results showed that slow speaking rate and vowel hyper-articulation significantly improved infants’ ability to recognize words, whereas wide pitch range did not. These findings suggest that 19-month-olds’ word recognition may be affected only by the linguistically relevant acoustic properties in IDS.

Received 23 December 2008Revised 07 April 2010Accepted 08 April 2010Published online 16 July 2010

Acknowledgments:

We thank Sheila Blumstein, Lori Rolfe, Elena Tenenbaum, Yen-Liang Shue, Julie Sedivy, and Melanie Cabral for assistance at the various stages of this work. This work was supported by NSF Grant No. BCS-0544127 and NIH Grant No. R01MH60922 to Katherine Demuth, and NIH Grant No. R01HD32005 to James Morgan.